Collectivity at the prolate-oblate transition:the 2₁⁺ lifetime of ¹⁹⁰W

The neutron-rich rare isotope 190W is discussed as a candidate for a prolate-oblate transitional nucleus with maximum γ-softness. The collectivity of this isotope is assessed for the first time by the measurement of the reduced E2 transition probability of its first 2+ state to the ground state. The experiment employed the FAst TIming Array (FATIMA), comprised of 36 LaBr3(Ce) scintillators, which was part of the DESPEC setup at GSI, Darmstadt. The 41+ and 21+ states of 190W were populated subsequently to the decay of its 127(12) μs isomeric Jπ  = 10- state. The mean lifetime of the 21+ state was determined to be τ = 274(28) ps, which corresponds to a B(E2; 21+ → 01+) value of 95(10) W.u. The results motivated a revision of previous calculations within an energy-density functional-based interacting boson model-2 approach, yielding E2 transition properties and spectroscopic quadrupole moments for tungsten isotopes. From comparison to theory, the new data suggest that 190W is at the transition from prolate to oblate structure along the W isotopic chain, which had previously been discussed as a nuclear shape-phase transition

Decay studies in the A ∼ 225 Po-Fr region from the DESPEC campaign at GSI in 2021

The HISPEC-DESPEC collaboration aims at investigating the structure of exotic nuclei formed in fragmentation reactions with decay spectroscopy measurements, as part of the FAIR Phase-0 campaign at GSI. This paper reports on first results of an experiment performed in spring 2021, with a focus on β-decay studies in the Po-Fr nuclei in the 220 < A < 230 island of octupole deformation exploiting the DESPEC setup. Ion-beta correlations and fast-timing techniques are being employed, giving an insight into this difficult-to-reach region. © 2022 Societa Italiana di Fisica. All rights reserved

Cross-section measurements of radiative proton-capture reactions in Cd-112 at energies of astrophysical interest

status: publishe

Cross-section measurements of radiative proton-capture reactions in Cd 112 at energies of astrophysical interest

Reactions involving the group of nuclei commonly known as p nuclei are part of the nucleosynthetic mechanisms at astrophysical sites. The In113 nucleus is such a case with several open questions regarding its origin at extreme stellar environments. In this paper, the experimental study of the cross sections of the radiative proton-capture reaction Cd112(p,γ)In113 is attempted for the first time at energies lying inside the Gamow window with an isotopically enriched Cd112 target. Two different techniques, the in-beam γ-ray spectroscopy and the activation method, have been applied. The latter method is required to account for the presence of a low-lying In113 isomer at 392 keV having a half-life of ≈100min. From the cross sections, the astrophysical S factors and the isomeric ratios have been additionally deduced. The experimental results are compared to detailed Hauser-Feshbach theoretical calculations using talys and discussed in terms of their significance to the optical model potential involved. © 2019 American Physical Society

An investigation of radiative proton-capture reactions in the Cd-In mass region

The reaction network in the neutron-deficient part of the nuclear chart around A similar to 100 contains several nuclei of importance to astrophysical processes, such as the p-process. This work reports on the results, from recent experimental studies of the radiative proton-capture reactions Cd-112,Cd-114 (p, gamma) In-113,In-115. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched Cd-112 and Cd-114 targets. Two different techniques, the in-beam gamma-ray spectroscopy and the activation method have been employed, with the latter considered necessary to account for the presence of low-lying isomers in In-113 (E-gamma approximate to 392 keV, t(1/2) approximate to 100 min), and In-115 (E-gamma approximate to 336 keV, t(1/2 )approximate to 4.5 h). Following the measurement of the total reaction cross sections, the astrophysical S factors have been additionally deduced. The experimental results are compared with Hauser-Feshbach theoretical calculations carried out with the most recent version of TALYS. The results are discussed in terms of their significance to the various parameters entering the models. (C) 2021 Elsevier B.V. All rights reserved

Radiative proton–capture reactions with 112,114Cd, at astrophysically important energies

Poster presented in the 16th International Symposium on Nuclei in the Cosmos (NIC XVI), 21-25 September 2021, China</p

Nuclear Structure Investigations in Yb isotopes

International audienceThe medium-to-heavy mass ytterbium isotopes (70Yb) in the rare-earth mass region are known to be well-deformed nuclei, which can be populated to very high spin, and are predicted to exhibit interesting phenomena, such as shape coexistence. The lack of any experimental information on the structure of the neutron-rich 180Yb isotope and the lifetime of the 21+ state of 178Yb have greatly motivated this study, which can offer useful information for the collective behavior of neutrons and protons in neutron-rich Yb isotopes. A measurement was performed to investigate the population of excited states and a first measurement of the unknown 21+ lifetime of 178Yb by means of a two neutron-transfer reaction 176Yb(18O,16O)178Yb at energies 68-74 MeV using the ROSPHERE array at IFIN-HH, Romania